class Solution {
public:
    void sortColors(vector<int>& nums) {
        int n = nums.size();
        int left = -1, right = n, i = 0;
        while (i < right)
        {
            if (nums[i] == 0) swap(nums[++left], nums[i++]);
            else if (nums[i] == 1) i++;
            else swap(nums[--right], nums[i]);
        }

    }
};